Editor’s pickAngkor may have collapsed more than five centuries ago, but the lessons it taught us are still relevant today

At its peak, Angkor, from the ancient Cambodian Khmer Empire, was one of the most powerful civilisations in the world and home to almost a million inhabitants, but the resource that made it was the very same that brought about its ruin.

Dan Penny, an environmental history expert and a researcher at the geosciences department in the University of Sydney, has studied the once-powerful Angkor civilisation for years, said that the site – which had been a bustling metropolis – is now a constant reminder that harnessing the power of water is instrumental in building, though water can also have a hand in destroying.

For a long time, the fall of the Angkor Empire was a mystery, but now, research scientists have revealed that an extended period of drought followed by severe monsoon rains in the area caused extensive damage to the infrastructure of the city, which led to its downfall.

There, a crumbling bridge constructed out of reused sandstone blocks, notable in its isolation stands. It may seem to be of little significance as there is no longer any water from the Siem Reap River running beneath it, but to Penny, it might as well be a goldmine.

“The destruction of this bridge is suggestive of a high flow of water, far more than the canal could cope with, coming down through the middle of the city,” Penny said to National Geographic. “It did a huge amount of damage to infrastructure that people who were living here at the time simply couldn’t repair.”

A city made by waterFrom the very first, Angkor was dependent on water for its development, and later came to be known as the “hydraulic city”. The metropolis boasted a stunning network of channels and reservoirs, all constructed in order to collect and store the water that came from the hills for both flood control and distribution for usage in agriculture and otherwise. Above all, a complex system of bypasses and overflows brought the excess water to the Tonlé Sap Lake, Cambodia’s largest inland lake.

“It was a water management infrastructure that had no equal on Earth,” Penny stated. “[The] water was not only a resource that had to be managed in terms of agriculture and flooding.”

That was because water, as well as its harnessing, played a role that was nothing short of religious in the city, bound up with the power of the ruling monarch, according to Penny.

The water network showed research scientists a history and timeline of additions, improvements, and modifications. The earlier channels simultaneously disposed of and distributed water to residents, but by the 12th century – approximately when the internationally-renowned temple, Angkor Wat, was constructed and the Empire hit its zenith – newer and larger channels were bringing the water back to the Tonlé Sap Lake.

Over the next century or so, as the metropolis continued to grow and flourish, the system performed well. But drought came to the region in the mid to late 1300s, tailed by exceptionally intense monsoon rains for a few years that produced floods. The city’s sophisticated infrastructure had not even been able to cope with the deluge.

A city broken by waterThe floods eroded the system, which shows signs of being “systematically severed,” according to National Geographic. Canals in the city were clogged with the eroded materials swept from the heart of Angkor.

The bridge was constructed around this time, built from intricately-carved stone blocks recycled from sacred temples.

“That they would take apart a temple and use it for something as mundane as a bridge suggests there is something seriously going wrong,” Penny explained. “It has long been though that the damage to the water management system put an end to a long period of decline at Angkor.”

But the bridge, damaged and crumbling, showed that efforts to control the waters were unsuccessful. The Siem Reap River that was supposed to originally flow beneath it instead carved the bridge away, and now runs approximately seven meters away from where it once was.

The floodwaters ruined the city’s infrastructure, and Angkor fell, hammered into oblivion by the climate. The military from Siam – now Thailand – captured the metropolis in 1431. The jungle then grew over many of the temples in the area, though some have continued to be important religious sites. And until French explorers were brought there in the 1860s, the ruins remained unknown to most of the world.

The lessons learnedAngkor highlights the intangible but undoubted connection between people and the climate, research scientists say, pointing to the valuable lessons the ruins offer.

“One thing is clear: Culture and climate are connected,” Sudeep Chandra, the director of the University of Nevada Global water Centre. “We see communities around the world struggle with understanding how to respond to the increased variability from a changing climate.”

In redirecting the flow of water from the existing river systems in their efforts to control and harness the resource, the Angkorian engineers had inadvertently created new water catchments which were detrimental to the environment, eventually undermining the city and leading to its fall.

“The medieval Khmer were confronted with a period of climatic instability that they had no experience of, and which fully changed the rules of the game that they had been playing for hundreds of years,” Penny concluded. “A similar scale of challenge is now confronting contemporary communities, as the climate begins to change.”